1 / 19

S-72.227 Digital Communication Systems

S-72.227 Digital Communication Systems. Fiber-optic Communications - Supplementary. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

hsweeney
Download Presentation

S-72.227 Digital Communication Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. S-72.227 Digital Communication Systems Fiber-optic Communications - Supplementary

  2. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  3. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  4. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  5. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  6. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  7. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  8. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  9. G. Keiser: Optical Fiber Communications, McGraw-Hill, 2nd Ed.

  10. EDFA - energy level diagram Fluoride class level(EDFFA) • Pump power injected at 980 nm causes spontaneous emission from E1 to E3 and there back to E2 • Due to the indicated spontaneous emission lifetimes population inversion (PI) obtained between E1 and E2 • The higher the PI to lower the amplified spontaneous emission (ASE) • Thermalization (distribution of Er3+ atoms) and Stark splitting cause each level to be splitted in class (not a crystal substance) -> a wide band of amplified wavelengths • Practical amplification range 1525 nm - 1570 nm, peak around 1530 nm E4 980 nm excited state absorption E3 Er3+ levels E2 1530 nm 980 nm 1480 nm E1

  11. 100 Fundamental limits of silica fibers 50 Water spike 10 5 Band Description Wavelength (nm) 1 Loss (dB/km) O-band Original 1260-1360 E-band Extended 1360-1460 S-band Short 1460-1530 C-band Conventional 1530-1565 L-band Long 1565-1625 U-band Ultra-long 1625-1675 0.5 0.1 Rayleigh scattering Infrared absorption 0.8 1.0 1.2 1.4 1.6 1.8 Wavelength (mm) • C-band: supports early EDFA • C+L-band: support for EDFA’s of today • Raman amplifiers can be used over all bands - new (medium loss) bands are now applicable (as S & U bands) • New fibers can reduce loss at E & S bands (however, EDFA does not work here & Raman gain small) • Inter- and Intra-modal dispersion • Attenuation (Loss) • Non-linear effects • Four-wave mixing (FWM) • Stimulated Raman & Brillouin scattering (SRS,SBS) • Cross-phase & self-phase modulation (SPM,XPM) • Polarization fluctuations

  12. Modulation of lasers

  13. LD distortion coefficients • Let us assume that an LD transfer curve distortion can be described bywhere x(t) is the modulation current and y(t) is the optical power • n:the order harmonic distortion is described by the distortion coefficientandFor the applied signal we assume and therefore

  14. Link calculations • In order to determine repeater spacing on should calculate • power budget • rise-time budget • Optical power loss due to junctions, connectors and fiber • One should be able to estimate required margins with respect of temperature, aging and stability • For rise-time budget one should take into account all the rise times in the link (tx, fiber, rx) • If the link does not fit into specifications • more repeaters • change components • change specifications • Often several design iteration turns are required

  15. Link calculations (cont.) • Specifications: transmission distance, data rate (BW), BER • Objectives is then to select • Multimode or single mode fiber: core size, refractive index profile, bandwidth or dispersion, attenuation, numerical aperture or mode-field diameter • LED or laser diode optical source: emission wavelength, spectral line width, output power, effective radiating area, emission pattern, number of emitting modes • PIN or avalanche photodiode: responsivity, operating wavelength, rise time, sensitivity FIBER: SOURCE: DETECTOR/RECEIVER:

  16. The bitrate-transmission length grid SI: step index, GI: graded index, MMF: multimode fiber, SMF: single mode fiber

  17. Using Mathcad to derive connection between fiber bandwidth and rise time

  18. Ref: A.B.Carlson: Communication Systems, 3rd ed

  19. Ref: A.B.Carlson: Communication Systems, 3rd ed

More Related